Underwater wall structure

ABSTRACT

A permanent underwater wall structure comprising a series of individual pilings driven into the ocean floor, serves in the process of shoreline accretion. The underwater wall structure consists of three portions. These are: two end portions extending from the shoreline to an offshore bar, and a connecting middle portion running generally along the length of the offshore bar and connecting the two middle portions. The individual pilings are driven into the ocean floor at such a depth that all except the pilings closest to the foreshore are beneath the waterline and are at the same height approximating the level of the top of the offshore bar. The underwater wall structure serves, then, to allow unimpeded flow of water toward the shore, but impedes the offshore and littoral currents laden with sediment so as to allow deposition of sediment within the area defined by the wall structure.

[ 5] Dec. 23, 1975 UNDERWATER WALL STRUCTURE Robert Newman Hebel, Jr., 5306 Bowling Green Drive, Fort Pierce, Fla. 33450 221 Filed: Aug. 13, 1974 21 Appl. No.: 496,935

[76] Inventor:

[52] US. Cl. 61/4; 6l/53.74; 61/59 [51] Int. Cl. E02B 3/04 [58] Field of Search 61/4, 5, 39, 50, 59, 53.74, 61/3, 49

[56] References Cited UNITED STATES PATENTS 346,140 7/1886 Bates 61/4 757,368 4/1904 Truax 61/4 942,653 12/1909 Louqur 61/59 1,371,709 3/1921 Stockfleth..... 61/39 1,870,154 8/1932 Wehr 61/4 1,877,113 9/1932 Young 61/4 X 2,069,715 2/1937 Arpin 61/4 2,348,508 5/1944 Wells 61/4 3,379,015 4/1968 Macks 61/4 3,835,651 9/1974 Butterworth et a1 61/4 3,844,125 10/1974 Williams, Sr ..61/4

Primary Examiner.lacob Shapiro Attorney, Agent, or Firm-Wm. R. Price [57] ABSTRACT A permanent underwater wall structure comprising a -series of individual pilings driven into the ocean floor,

serves in the process of shoreline accretion. The underwater wall structure consists of three portions. These are: two end portions extending from the shoreline to an offshore bar, and a connecting middle portion running generally along the length of the offshore bar and connecting the two middle portions. The individual pilings are driven into the ocean floor at such a depth that all except the pilings closest to the foreshore are beneath the waterline and are at the same height approximating the level of the top of the offshore bar. The underwater wall structure serves, then, to allow unimpeded flow of water toward the shore, but impedes the offshore and littoral currents laden with sediment so as to allow deposition of sediment within the area defined by the wall structure.

7 Claims, 8 Drawing Figures US. Patent D6C.23, 1975 Sheet 1 of4 3,927,533

FIG. I

U.S. Patent Dec. 23, 1975 Sheet20f4 3,927,533

Sheet 3 of 4 3,927,533

US. Patent Dec. 23, 1975 FIG. 4

U.S. Patent Dec. 23, 1975 Sheet4 0f4 3,927,533

UNDERWATER WALL STRUCTURE FIELD OF THE INVENTION This invention relates to a permanent underwater 5 wall structure for use in the process of accretion along sea shores and beaches subject to erosion. More specifically, this invention relates to a structure installed beneath the surface of the water at mean low tide along a shore-line where erosion has already begun. Still more specifically, this invention relates to the provision of a permanent underwater wall structure along a beach characterized by an offshore sand bar, a longshore trough and which consists of two end sections and a middle section. The middle section extends generally along the direction of said offshore bar.

DESCRIPTION OF THE PRIOR ART The problem of seashore erosion in certain areas of the country has serious economic ramifications. Beaches normally are either prograding, remaining neutral or retrograding. Owing to a combination of tide, waves, ground water, evaporation and seepage, the porosity of shore material changes. In addition, the waves and wind are powerful sorting tools. Sediment size will vary considerably along any profile across the beach and along any contour along a beach.

Various approaches have been proposed for eliminating seashore erosion, these have included, breakwaters, jettys, and groins. The problem with breakwaters is the fact that they must be of enormous size and consequently are extremely expensive. Thus', for example, offshore rubble mounds of breakwaters contain armor pieces on top of the mound in sizes of from ten to twenty tons. Additionally some concrete blocks have been cast in sizes of up to forty tons. This is because the breakwaters have been built to extend above the water line and thus are subjected to the enormous forces of the pounding surf.

For this reason, much of the seashore erosion in parts of the country have gone unimpeded and in certain areas, vast quantities of beaches have been washed away without any great success in stopping the erosion much less reversing the process to one of shoreline accretion.

SUMMARY OF THE INVENTION According to this invention, a permanent underwater wall structure is provided along a shoreline characterized by an ofishore bar and a longshore trough. This shore contour normally is indicative of the fact that the erosion process has begun with the formation of the offshore bar from the material from the foreshore portion of the beach. This invention is applicable to shore contours in which the offshore bar is no more than 150 feet from the normal shoreline at mean low tide. According to this invention, the permanent underwater wall structure comprises individual pilings driven in side-by-side relation into the ocean floor consisting of three sections. These are, two end section which extend in spaced-apart relation from the vicinity of the shoreline, some 150 feet to the offshore bar and a middle connecting section extending generally along the offshore bar and connecting the two end section. The individual pilings are driven to such a depth that all except the pilings adjacent to the shoreline are below the water level at mean low tide and generally are in a horizontal plane with the top of the ofishore bar. For this reason, the flow of water toward the beach is unimpeded while the offshore and littoral currents carrying suspended material away are impeded thus allowing deposition of suspended material within the protected areas. Interlocking tongue and groove and guiding joints are provided for locking and guiding the individual pilings so as to form a unitary contiguous structure. Additionally, a method of hydraulically displacing the sediment to provide for gravitational placement of the pilings into the ocean floor is disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of one embodiment of the present invention illustrating the conformation of the un- .derwater wall structure in relation to the shoreline and in relation to the offshore bar.

FIG. 2 is a sectional view along lines 22 of FIG. 1 illustrating partially, in section, the underwater wall structure.

FIG. 3 is a view illustrating in full lines the ocean floor profile illustrated in FIG. 2 and illustrating in phantom lines, the foreshore area formed by the process of shoreline accretion and the concommitant formation offshore of a new offshore bar and longshore trough.

FIG. 4 is a front elevational view of the individual piling used in the formation of the underwater wall of the invention.

FIG. 5 is a sectional view of the pilings taken along lines 5-5 of FIG. 4.

FIG. 6 is a plan view of another embodiment of the underwater wall of this invention illustrating a rectangular configuration.

FIG. 7 is a sectional view taken along lines 77 of FIG. 6 illustrating the angle at which individual pilings are driven, and,

FIG. 8 is a fragmentary view illustrating the method of hydraulically driving the pilings into the ocean floor.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail, the shoreline 1 extends into the water to form a sloping floor 2 having an offshore trough 3 next to the offshore bar 4. As has been previously indicated, this invention is applicable to instances in which the offshore bar 4 is feet or less from the shoreline 1 at mean low tide. In FIG. 2 the offshore ocean swell 5 forms into an ocean wave 6, thence into a peaking wave 7 which breaks at point 8. Normally an ocean wave breaks when it enters shallow water. In the. diagram shown in FIG. 2, the solid line indicates the base of the waves. In deep water, the height of the ocean swell 5 is approximately l/20 of its length, dimension A, which normally is defined as the horizontal distance between successive crests. As the waves enter shallow water, the drag of the bottom 2 shortens the wave length, dimension B, to twice the depth of the water, dimension C. This forces the wave to a peak D. The peaking wave 7, breaks when its height E is about equal with the water depth F. This occurs generally at the highest point of the offshore bar thus producing a tremendous rush of surf into the fore shore area of the beach. The wave motion creates a tremendous turbulence which places material in suspension and the current carries the suspended material and rolls the heavy bottom material from place to place. Since the waves break at a small angle to the beach, a wave induced current is set up that flows along the beach. This current is called the littoral or longshore current, resulting in the longshore trough 3 adjacent to the offshore bar 4. In general, erosion is most severe when large waves occur during high water level while similar wave action during low water may build the beach. This is partially due to the fact that the point at which the waves break varies with the height of the wave and the depth of the water. Thus, once an equilibrium is set up, breaking of the waves at a different point upsets the equilibrium and therefore places voluminous quantities of material and sediment in suspension. Once this process starts, the longshore or littoral current along the longshore trough can transport tremendous masses of material. The direction of longshore movement or littoral drift, varies with the direction of the wind. n most coasts, however, there is a prevailing direction which can be determined from typical formations on the coast.

According to the present invention, the wall structure consisting of end sections and middle section 12 comprises a series of individual concrete pilings driven into the floor 2 of the ocean floor. The middle section 12 as illustrated in FIG. 2, is driven to a height approximately equal to the highest point of the offshore bar 4. Thus, the underwater wall structure does not impede the flow of the breakers towards shore. Further, unlike the prior art breakwaters and jettys, the underwater wall structure is not subjected to the full force of the pounding surf upon the wall. Consequently, the water of the pounding breakers 8 passes over the top of the middle section 12 of the wall structure and goes inward carrying with it the sediment. The end section 10 of the wall structure impedes the littoral currents in either direction. The offshore current is impeded by the middle section 12 to such an extent that the suspended sediment is allowed to deposit within the protected area.

Since a good portion of the material in suspension will carry over the top of the wall structure, there is gradually built a relatively stable, sloping beach from the existing shoreline l to the point 20, Le, the point of the orignial middle section of the underwater wall structure. As the process of accretion develops, additional sediment is carried outside of the original walled in area and thus allows the formation of an identical ocean floor contour 2 shown in phantom lines in FIG. 2 which can be subsequently fitted with another underwater wall structure to proceed with the process of accretion.

The individual pilings consist of a concrete slab four inches thick and fabricated of 3,000 pound cement containing reinforced steel vertical rods 21 and horizontal steel rods 22, welded at point 23. The offshore surface of the front face contains vertical corrugations 25, while in a preferred embodiment the foreshore face 26 is smooth. Each of the concrete pilings 20 contains a guiding and locking groove 30 on one side and a complementary vertically disposed tongue 31 on the other edge. If it is desired to drive the concrete pilings into the ocean floor by means of a pile driver, a steel cap 33 may be utilized. In such instance, a steel rod bent and welded to the cap forming a handle 34 may be utilized to assist in picking up the heavy concrete pilings and moving them from place to place. The concrete pilings 20 are tapered at points 36 and 37 to a general point 38. The taper on side 37 is not as great as the angle of taper on side 36. Thus if a vertical line is run from the edge of the point 38, an angle 39 is produced between the tapered edge and the vertical lines, which is greater than the angle 40 running from a vertical line extending from the point 38 to the corre sponding tapered edge 36. This allows, clue to the greater angle 39 on the tapered side 37, pressure to be exerted in the direction of the arrow so that the groove 30 is driven into closer engagement with the complementary tongue 31 on an adjacent piling.

As will be seen by reference to FIG. 6, the underwater sea structure can be built in other than an arc-like configuration. Thus, the end wall section 10 may be built in essentially a straight line which connects with the connecting wall section 12 running in a straight line along the offshore bar 4. In this instance, however, it is necessary to form at least one of the end wall section 10, at a slight angle so as to deflect some of the littoral current in the prevailing direction.

Generally speaking, in the area of Fort Pierce, Florida, the prevailing littoral current is from north to south. A current running, then from south to north, normally acts to erode the beach. Thus in this area, the southern end wall section 10 would be directed at a slight angle relative to the middle section 12 of the underwater structure. Further, if the middle section 12 extends in essentially a straight line along the length of the bar 4, I have found it is best to drive the pilings at an angle directed toward the beach within the range of 45 to Actually an angle in the range of 55 to 75 is preferred and the angle illustrated in FIG. 7 is approximately 70 from a horizontal line projected from the sand bar 4. Driving the pilings at this angle allows the onrushing surf to surge over the top of the angularly disposed pilings 20 along the vertical corrugations 25 and into the protected area. Sediment in the ofishore and littoral currents then is impeded sufficiently long as the currents flow over the top of the pilings in sections 10 and middle section 12 of the underwater wall structure so as to allow the majority of the sediment to be deposited onto the floor 2 of the ocean.

It will be clear to those skilled in the art, that as the contour of the ocean floor changes, and as the bar 4 begins to grow in a offshore direction, the point at which the waves break will change, thus changing again the contour of the ocean floor of the wall structure W. After a period of time, a smooth beach will form from the original shoreline to the point at which the original pilings were driven and the ocean floor 2 off-shore from this point will take on a profile almost identical to the original. At this time a new wall structure can be installed extending from the new shoreline, out some feet to the newly formed sand bar and the entire process of the shore accretion can be resumed.

As has been mentioned, one method of driving the pilings into position that has been indicated is a pile driver. A preferred method, however, illustrated in FIG. 8, involves the use of a hose 10 through which a jet of high pressure water can be inserted at the top of the pilings. As is shown, the hydraulic forces 61 emitting from hose 60 forces the sediment 62 away from the point 38 of the pilings so that the weight of the piling will move gravitationally to the opening formed thereby.

Therefore, all that is required is the services of a scuba diver and a large pump which can pump sea water from the ocean into the 4 inch hose 60 directed to the point of insertion of the tapered ends 36 and 37 of the concrete slab 20.

Many modifications will occur to those skilled in the art from the detailed description hereinabove given and such is meant to be exemplary in nature and nonlimiting except so as to be commensurate in scope with the appended claims.

I claim:

1. For use in the process of shoreline accretion along a beach having an offshore bar, located no further than 150 feet offshore from said beach, and a longshore trough, immediately adjacent to said offshore bar;

A. a permanent underwater wall structure located between said bar and said beach at a point shoreward of where the waves normally break; said wall structure comprising a series of individual pilings in side-by-side relation,

1. each of said pilings being embedded at one end in the ocean floor, at such a depth that the top of each of the offshore pilings is below the water level at mean low tide, and is no higher than the highest point of said offshore bar;

B. said underwater wall structure comprising two end sections and a connecting middle section,

1. said end sections located in spaced apart relation, extending seawardly no more that 150 feet, from the vicinity of said beach and through said trough to said offshore bar,

2. said middle section extending along said bar, between said longshore trough and said offshore bar and connecting each of said end sections to form a contiguous, unitary, underwater wall structure;

3. said underwater wall structure serving to allow an unimpeded flow of water shoreward, but impeding the offshore and littoral currents sufficiently to allow deposition of suspended particles within the are bounded by said wall structure.

2. A permanent underwater wall structure, as defined in claim 1,

A. The further improvement in which the shoreward ends of said end sections comprise pilings driven into the ocean floor but which extend above the water level as each end section into proximity to the shoreline.

3. A permanent underwater wall structure, as defined in claim 1,

A. in which at least one of said end sections extends at an acute angle from the shoreline to said middle section of said underwater wall structure, and which forms an oblique angle with said middle section;

B. said end section being located opposite to normal 5 flow of the littoral current for said shoreline.

4. A permanent underwater wall structure, as defined in claim 1, in which:

A. said middle section of said wall structure extends along said bar in a line generally parallel to said beach, and in which:

ll said pilings forming said middle section are angularly disposed toward said beach,

2. the angle formed between each of said pilings and a horizontal line projected shorewardly from the base of the said bar, being in the range of some 45 to 90.

5. A permanent underwater wall structure, as defined in claim 4, in which,

A. said middle section of said wall structure extends in a straight line along said bar and in a line generally parallel to said beach, and,

B. in which the individual pilings are disposed at an angle towards the shore of between 55 and 75.

5 6. A permanent underwater wall structure, as defined in claim 1, in which:

A. each of said pilings is a reinforced concrete slab including:

1. a locking and guiding groove on one vertical edge and,

2. a complementary tongue of the other vertical edge for interlocking engagement with adjacent pilings, and,

3. a tapered end portion forming a point, in which the angle of the tapered edge on one side is greater than the angle of the tapred edge on the other side. 7. A permanent underwater wall structure, as defined in claim 1, in which,

A. each of said end sections extend from the shoreline to said offshore bar in the form of a curved arc and,

B. said middle section extends in the form of an arc along said bar. 

1. For use in the process of shoreline accretion along a beach having an offshore bar, located no further than 150 feet offshore from said beach, and a longshore trough, immediately adjacent to said offshore bar; A. a permanent underwater wall structure located between said bar and said beach at a point shoreward of where the waves normally bReak; said wall structure comprising a series of individual pilings in side-by-side relation,
 1. each of said pilings being embedded at one end in the ocean floor, at such a depth that the top of each of the offshore pilings is below the water level at mean low tide, and is no higher than the highest point of said offshore bar; B. said underwater wall structure comprising two end sections and a connecting middle section,
 1. said end sections located in spaced apart relation, extending seawardly no more that 150 feet, from the vicinity of said beach and through said trough to said offshore bar,
 2. said middle section extending along said bar, between said longshore trough and said offshore bar and connecting each of said end sections to form a contiguous, unitary, underwater wall structure;
 3. said underwater wall structure serving to allow an unimpeded flow of water shoreward, but impeding the offshore and littoral currents sufficiently to allow deposition of suspended particles within the are bounded by said wall structure.
 2. said middle section extending along said bar, between said longshore trough and said offshore bar and connecting each of said end sections to form a contiguous, unitary, underwater wall structure;
 2. A permanent underwater wall structure, as defined in claim 1, A. The further improvement in which the shoreward ends of said end sections comprise pilings driven into the ocean floor but which extend above the water level as each end section into proximity to the shoreline.
 2. a complementary tongue of the other vertical edge for interlocking engagement with adjacent pilings, and,
 2. the angle formed between each of said pilings and a horizontal line projected shorewardly from the base of the said bar, being in the range of some 45* to 90*.
 3. A permanent underwater wall structure, as defined in claim 1, A. in which at least one of said end sections extends at an acute angle from the shoreline to said middle section of said underwater wall structure, and which forms an oblique angle with said middle section; B. said end section being located opposite to normal flow of the littoral current for said shoreline.
 3. a tapered end portion forming a point, in which the angle of the tapered edge on one side is greater than the angle of the tapred edge on the other side.
 3. said underwater wall structure serving to allow an unimpeded flow of water shoreward, but impeding the offshore and littoral currents sufficiently to allow deposition of suspended particles within the are bounded by said wall structure.
 4. A permanent underwater wall structure, as defined in claim 1, in which: A. said middle section of said wall structure extends along said bar in a line generally parallel to said beach, and in which:
 5. A permanent underwater wall structure, as defined in claim 4, in which, A. said middle section of said wall structure extends in a straight line along said bar and in a line generally parallel to said beach, and, B. in which the individual pilings are disposed at an angle towards the shore of between 55* and 75*.
 6. A permanent underwater wall structure, as defined in claim 1, in which: A. each of said pilings is a reinforced concrete slab including:
 7. A permanent underwater wall structure, as defined in claim 1, in which, A. each of said end sections extend from the shoreline to said offshore bar in the form of a curved arc and, B. said middle section extends in the form of an arc along said bar. 